I mean, they essentially operated 9 of every 10 refineries. That was enough for both the NJ and US courts to deem them a monopoly (yes, they used those words).[1]

And since a monopoly is just “certain business practices” that unfairly constrain competition, your definition seems to be a difference without a distinction.

[1] Standard Oil Co. of New Jersey v. United States, 221 U.S. 1 (1911)

SO's market share declined substantially throughout the trial. How does that fit your thesis?

See "Titan" by Chernow.

If you agree that more risk tends to push prices lower with all else being equal, I don’t see that being indicative of evidence considering investors would presumably be pricing in regulation risk.

But in any event the price at trial is not necessarily indicative of unfair anti-competitive business practices. The trial was not necessarily about the current practices at the time of the trial, but broke the business practices into three distinct periods dating back to 1870.

Why did SO's "natural monopoly" keep sliding away from them throughout the trial period?

I don’t think you’re tracking. There’s no guarantee a natural monopoly will remain in place forever or reuse we’d still be working by whale blubber light. What happened to the business during the trial is not necessarily relevant to the trial ruling.

I think a better question for you to ask yourself is “why did the court determine they were acting in a monopolistic manner?”

I’d suggest reading the previously referenced court ruling to get your answer.

If you want to call SO a "natural monopoly", the evidence does not support that conclusion. Nor did the trial conclude SO was a monopoly. That's my point here.

Rockefeller was convicted of being rich. That's the bottom line.

Except multiple courts disagree with your conclusion and found Standard Oil guilty of anti-competitive price fixing. Meaning they found evidence to the contrary of your point.

Here is a part of the majority court decision written by Chief Justice White:

"constituted a combination in violation of the first section and an attempt to create a monopoly or to monopolize"

See the word "attempt". That changes everything. They were not convicted of having a monopoly.

Uh, no. Feel free to read the actual referenced judicial opinion rather than cherry-picking to suit your conclusion. That was the word used in the charge. Here's more of it:

>"entered into agreements with, various persons, firms, corporations, and limited partnerships engaged in purchasing, shipping, refining, and selling petroleum and its products among the various states, for the purpose of fixing the price of crude and refined oil and the products thereof, limiting the production thereof, and controlling the transportation therein, and thereby restraining trade and commerce among the several states, and monopolizing the said commerce"

If actual price-fixing to monopolize commerce isn't part of your unique definition of a monopoly, I don't know what else to tell you. It's pretty hard to price fix without a monopoly, but as we already discussed they were able to do so because they controlled over 90% of refineries at the time. (And before you jump in again - erroneously - about their price during the trial, this monopoly charge was related to actions decades earlier). But it's pretty obvious from your relentless rules-lawyering/wordsmithing that either you aren't responding in good faith or don't actually have the ability/willingness to read evidence objectively.

Cognitive dissonance is a hell of a drug.